1) Prep pans and oven
Heat oven to 350°F. Grease two 8-inch round cake pans, line bottoms with parchment, then grease the parchment. Flour the pans lightly and tap out excess.
Note: This recipe is written for two 8-inch layers. If you use 9-inch pans, the layers will be a bit shorter and may bake a few minutes faster, so start checking early.
2) Mix dry ingredients
In a bowl, whisk together cake flour, baking powder, baking soda, and salt.
3) Cream butter and sugar
In a stand mixer (or with a hand mixer), beat butter and sugar on medium-high until light and fluffy, about 3 to 4 minutes. Scrape the bowl.
4) Add eggs and flavor
Add eggs one at a time, mixing well after each. Mix in vanilla and almond extract.
5) Add buttermilk and sour cream, then flour
Whisk buttermilk and sour cream together until smooth. Add the dry ingredients in three additions, alternating with the buttermilk mixture in two additions. Start and end with dry ingredients. Mix on low just until combined. Do not overmix.
6) Bake
Divide batter evenly between pans and smooth the tops. Bake for 26 to 30 minutes, until a toothpick comes out clean or with a few moist crumbs.
Cool in pans 10 minutes, then turn out onto a rack to cool completely.
Cooling note: “Completely” matters here. Warm cake + whipped frosting = slip-and-slide. Plan on 1 to 2 hours for full cooling (timing varies by kitchen).
7) Macerate the berries
In a bowl, toss strawberries, blueberries, and raspberries with sugar, lemon juice, and zest. Let sit 15 minutes. Then drain off excess juice so your cake layers stay stable. You are aiming for berries that look glossy and juicy, but not swimming. Save the juice for spooning over yogurt or ice cream.
8) Make the frosting
This makes enough frosting to fill and frost a two-layer 8-inch cake.
In a large bowl, beat mascarpone and cream cheese on medium just until smooth, about 30 to 45 seconds. Keep it brief and do not overbeat.
Add powdered sugar, vanilla, and salt and mix until combined.
With mixer on low, slowly stream in the cold heavy cream, then increase to medium-high and whip until medium-stiff peaks form. Stop as soon as it holds its shape. Overwhipping can make it grainy, and then it can break.
9) Assemble
If needed, level cake layers with a serrated knife. Place one layer on a cake stand or plate. Spread a generous layer of frosting on top, then add a layer of drained berries. Add a thin swipe of frosting over the berries to lock them in.
Top with the second cake layer. Apply a thin crumb coat, chill 15 minutes, then frost the cake fully.
10) Finish and serve
Top with fresh berries right before serving. Chill the assembled cake at least 30 minutes to set, then slice with a sharp knife wiped clean between cuts.
Make-ahead notes
Cake layers: Bake, cool completely, wrap well, and refrigerate up to 1 day (or freeze up to 2 months).
Frosting: Best made the day you assemble for the fluffiest texture.
Assembled cake: You can assemble up to 6 to 8 hours ahead and refrigerate. Add the final berry topping right before serving for the prettiest finish.
